Patent Document 1 listed below discloses a communication apparatus having a battery charger built therein. The battery charger includes an AC/DC converter for converting an AC voltage of AC100V that is supplied through a plug blade into a DC voltage having a predetermined voltage. The AC/DC converter is configured by using a switching regulator. The AC/DC converter performs a voltage conversion operation while a telephone main body block is not performing a reception operation, and at a time point when the telephone main body block starts the reception operation, stops the voltage conversion operation. According to the disclosure, this can prevent transmission and reception from being adversely affected by noise resulting from the switching regulator.
Patent Document 2 listed below discloses a radio selective calling receiver. A power circuit of this receiver includes a DC/DC converter. Until the receiver is synchronized with a POCSAG (Post Office Code Standardization Advisory group) signal, the DC/DC converter is turned on only for a last few msec immediately before a radio section of the receiver is turned on. On the other hand, after the receiver is synchronized with the POCSAG signal, the DC/DC converter is turned on a time period for receiving a synchronization signal in second and subsequent batches. The radio section is configured to receive a synchronization signal in a first batch but not to receive synchronization signals in the second and subsequent batches (that is, to be turned off). In this manner, when the radio section is in on-state, the DC/DC converter is turned off. According to the disclosure, this can eliminate an influence of noise caused by switching of the DC/DC converter.